According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.

It seems that a number of folks have missed one of the more important conclusions from our first paper on the surfacestations project. Co-author Dr. John Nielsen-Gammon has some things to say about it the finding that is the title.

For layman readers that don’t know what diurnal variation is, it is the daily variation of temperature due to the variation of incoming solar radiation from rotation of the earth on its axis.

Our paper has a lot of info and analysis about temperatures and temperature trends and their correspondence to siting class. Perhaps the most important question, “Is the mean temperature trend different from previous estimates?” is answered in the negative, albeit with an asterisk associated with the limited scope of the study. While negative results are useful, they’re also boring. So in this post I’ll talk about something we did learn about the climate that’s new and different, and why I think it matters.

This new finding is stated succinctly in the abstract as: “According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.”

The diurnal temperature range is simply the difference between the daily maximum temperature and daily minimum temperature, “diurnal” being a more impressive way of saying “daily”. It’s conventionally abbreviated DTR.

…

The change in global DTR trends roughly coincides with the change in phase of the Pacific Decadal Oscillation, for example, so it’s hard to tell whether the DTR trends were natural or forced.

That’s where Fall et al. 2011 comes in. The figure below shows the change in DTR anomalies over time over the United States, as estimated using data from each of the four classes of station siting. The data goes all the way back to 1895, making this (as far as we know) the longest evaluation of regional DTR trends done anywhere.

Dotted lines represent average values and are plotted 1.5 C apart from each other

All four classes of stations show the decline from the 1950s through the 1970s. But if you take a broader view, you see that the black line, representing the estimate from the best-sited stations, has a long-term positive (!) trend using unadjusted data or time-of-observation adjusted data, and has no trend at all for fully adjusted data (top set of curves). The lower-quality siting classes all show a negative long-term trend, and the worse the siting, the larger the trend.

These results suggest that the DTR in the United States has not decreased due to global warming, and that analyses to the contrary were at least partly contaminated by station siting problems. Indeed, DTR tended to increase when temperatures were fairly stable and tended to decrease when temperatures rose. Maybe DTR really isn’t a robust signal of global warming, and maybe the discrepancy between models and observations is primarily a problem with the observations rather than the models!

I’ve used the words “suggest” and “maybe” here. That’s because I regard our results as tentative. The zero trend estimate is based on only 80 stations, which might be only marginally adequate. The systematic change in trend with station siting quality makes me more confident, but the fact that the closest poorly-sited stations have a weak but positive DTR trend suggests that DTR may be strongly site-specific and makes me less confident. Maybe the best-sited stations have actually improved their siting over time, and maybe the adjustments haven’t fully corrected for this. Because of all this, I think these results need to be confirmed through other means or in other parts of the world before I will wholeheartedly believe that the real DTR has not been decreasing.

Nonetheless, all the ongoing work to understand the consequences of a faster rise in minimum than maximum temperatures for ecosystems and human health might, just might, be misguided.

67 thoughts on “According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.”

Can I applaud you and your colleagues for your labour of love in trying firstly to identify the best sited, maintained and monitored weather stations and secondly to carry out analyses to show that by determining which set of weather stations you use in your analyses, you may determine what conclusions you are going to draw.

I hope that the next 50 years sees the standards you have set rolled out globally in order that any scientific conclusions drawn about our climatic patterns are based on the best standards of data capture, comparison and standardisation.

I do not believe that temperature, due to your discovered difficulties of measurement, and the fudging which seems to continue despite the arguments against such questionable practice, is a good indicator of human effect on climate. Despite this, Anthony, your painstaking research on the siting of the surface stations has opened many peoples eyes to the many problems of data gathering. Well Done!

I’m surprised at the usage you’ve made of the surface station data. The siting data is only a snapshot of the history of the sites. What is now a 1 may have been a 5 or a 5 a 1 historically due to either changes in the site location or site relocation. Your analysis seems to imply a static situation which I don’t think is supportable. Consider Washington National airport. When built in the 1940’s Washington was a sleepy southern town that shut down in the summer. Now the airport is surrounded by concrete and asphalt and is basically in the middle of an urban area. I think there is too much uncertainty in the historical siting to make the inferences you’re making.

What interests me in the best sited stations is:
1. What is the trend for maximum daytime temperatures (both annually and month by month).
2. What is the trend for minimum night time temperatures (both annually and month by month).
3. How does this correspond with their counterparts in the entire station series.

Can someone remind me again why the tax-funded IPCC, ‘Climate Scientists’ or GISS cannot or did not do such a study. The Dutch had to get a private firm invovled before anyone took notice, in NZ it was said that actually their temp series wasn’t really a temp series and then over in the US you have to have individuals give up their free time to do such studies. I will not even comment on the MET/CRU here in blighty.

I guess when people are just simply handing you money hand over fist it’s too much bother to actually do an in-depth study before you have politico’s declaring that they will cut CO2 emissions by 80% in 20/30 years and all the economic hardships this puts on the poorest in our society.

Maybe the best-sited stations have actually improved their siting over time

So what? I read the post and stand by my comment. Using present conditions to extrapolate that the sites have the same conditions in the past is wrong. Especially when the location is not the same historically. Assuming that the site location has remained static you might assume that the microsite state is constant but only during that timeframe taking the data back to 1900 assuming that the CRN value is constant is making a big leap in my opinion especially if the site location has changed. Showing the data for the static siting timeframe would have more validity.

I spent four summers planting trees in Northern Ontario (Canada) – a completely forested area the size of France (maybe bigger). We lived and laboured outdoors 24/7 so we were very much in touch with the elements. We worked in huge clear-cuts, which were surrounded by the remaining forest. Late afternoon was the time I looked forward to with dread. It was almost always the hottest time of the day. The wind would die down, the sun would still blaze (albeit at a higher angle of incidence), and we toiled in the latent heat that accumulated throughout the day. Not a very scientific explanation, I realize, but the lag in temp. between noon and 3 – 5 P.M makes sense to me.

Yes, heat inertia in ground. Once did an experiment related to radon release mechanisms near a uranium mine, by using long stem thermometers set at different depths near Darwin Australia. There is a pronounced lag after the surface warms, before it warms at 20 cm depth (IIRC, the deepest we went) and then a later lag as it cools, of about the same duration. Unfortunately, I think the data were lost in a corporate takeover.

One question/observation regarding high temp of the day has a correlation in the low temp of the day. The lowest temp of a day is typically 30 – 45 minutes after sunrise, sometimes an hour. My basic understanding of this has to do with atmospheric heating and the change in wind direction. This causes the cooler air to blow from where the sun has not risen yet, blowing from cooler air masses to warmer air masses I wonder if there is a correlation in that at some point after noon, perhaps there is sufficient heating to cause the winds to blow from warmer air masses to cooler air masses until 5 pm’ish.
Anyway, just my $.02 worth…

Using DTR as a single analog for global warming is fraught with potential problems. There are other influences that must be accounted for before reaching any conclusions. For example:
1. There could be global warming (or cooling) and the DTR remain constant if the driving force(s) affected both night and daytime temperatures equally.
2. The daytime temperature could go up (or down) or the nighttime temperature could go up (or down).
3. Natural cycles such as ENSO affect humidity which plays a role in heat transfer.
4. Natural cycles affect winds which play a role in heat transfer.
5. Shielding may affect daytime temperatures more than nighttime temperatures.
6. From a harm to earth perspective, increasing daytime temperatures are more critical than increasing nighttime temperatures. DTR does not capture this aspect.

While one always tries to make answers as simple as possible, DTR seems too simple to me to fully explain changes in the temperature of the atmosphere. Less I sound too critical, earlier I expressed appreciation to the whole team who did the work and published the paper on the impact of measurement stations on climate change. I repeat my thanks.

BarryW has a reasonable point so what sort of result would the following give?

Take the current best 80 and the current worst 80. I’d suggest that the best 80 had tended to get better not worse on average over time and the worst 80 now would have tended to get worse on average over time. Reasonable?

Then plot the 2 sets of data and see how they differ. That would give an insight into how improvements and degradation affect the trends if at all.

For the diurnal charts at the beginning of the post, just noting that the temperature change is exaggerated by quite a bit in these charts compared to a real-world station. There is far less change in the actual energy levels/temperature at the surface over a 24 hour period (between Max and Min), than should be expected.

For the large differences in diurnal patterns that is found in Fall et al., there has to be quite large energy changes in terms of Watts/m2.

“In response to the ‘why lag?’ comment – as long as incoming radiation exceeds outgoing radiation (as per the second graph), temperature will rise.”

True only if heat lost from evaporation and conduction remains constant. But if e.g. the wind started to blow and there was significant loss from evaporation and conduction, then even at midday the temperature could drop.

And as I’m being pedantic, there is heat flow from the ground/sea … etc.

John, I see a question on you graph asking “Why the lag?”. Is that really a question?

To me that is because the insolation rate is still greater than the total upwelling surface energy rate lost to space, up until about 3 PM to 4PM. That point in the afternoon is when the insolation equals the outgoing.

These hourly breakdowns show that very affect. In these that lag was set be me (probably 1½ hours too late) to 5 PM as a rough guess:http://i56.tinypic.com/avc5g.jpg : KT97http://i53.tinypic.com/ir6lie.jpg : TFK09
Look at the point where the “Mean Surface Temperature” reverse and start to drop in the afternoon and then look notice the relation of incoming and outgoing energy fluxes. No adjustments for and thermal inertia were included in these figures, just a rough cosine weighted breakdown.

BTW: Thanks for giving the DTR some real scrutiny. Much deeper analysis on this needs to be performed for any re-siting where changes in the ground cover can affect this (IMHO) along with changes in the proximity to UHI sources and even where the site is located in relation to the seasonal prevailed winds. I have always felt they all affect the diurnal range and not necessarily in the same direction.
REPLY: Not his graph, I added it. Note the source link below it – Anthony

I also worked in northern Ontario (Timmins Region and points north, west, and south) in the early 1980’s. While I agree that the later afternoons were the warmest, I looked forward to them for the simple reason that the 500 quadrillion things that bite (blackflies and mosquitoes, mostly) don’t like it hot and dry.

Give me heat instead of clouds of insects flying up your nose, into ears and mouth, hair, and climbing under clothing to suck your blood.

There is no mystery regarding the lag in temperature with respect to peak insolation. Andrew Dodds points out correctly that – “as long as incoming radiation exceeds outgoing radiation (as per the second graph), temperature will rise”.

This is important when discussing the active sun hypothesis and the silly argument from climate ” scientists” that the temperature does not correlate with insolation. As Anthony has tried to explain before we should not expect it to correlate. An active sun means an increase in the energy released. The change in insolation at the top of the atmosphere is known to be small but its impact may be amplified by things like reduced cloud seeding (Svenmark). The extra energy reaching the surface causes an increase in temperature which results in an increase in outgoing radiation just the same as in the diurnal case. The overall temperature (I will not call it average temperature because it it not really the average which controls the energy balance) will increase until the outgoing radiation equals the incoming radiation. Because the sea is by far the most dominant source of radiation to space (either directly or after evaporation and other forms of atmospheric heating ) and since it takes such a long time to warm up, temperatures will continue to rise for years after the peak insolation. Indeed temperatures will continue to rise for most of the time that the sun remains above average output.

This is certainly not proof that the sun is the cause of any warming we have seen but it does make a nonsense of the claim that is cannot be the cause of the warming because the temperatures did not decline when the sun’s output declined.

But should we expect to see a century-scale trend? It’s clear that the primary cause of the 1880-1940 temp increase was due to solar effects rather than greenhouse, which should increase (not decrease) DTR. So the expected decrease in DTR should not be apparent until the LLGG forcing predominates, which didn’t happen until roughly 1970 or so. Therefore the expected DTR decrease should not be expected on the century scale (at least not yet), but only on shorter timescales.

Since the poorly-sited stations would seem to have an instrument-change bias that infects DTR, it would be quite useful to have a 30-year running average for DTR from the best-sited stations, or at least a data source for the same.

I am struggling with this data and need to look at it when I am less tired. Some sort of units on the y axis would be helpful. I don’t think I can see any meaningful trend in any of the data sets… Like everything else in climate science it seems to be a highly derivative measurable that can be affected by many variables, and very little to do with the point people are trying to make about humans adversely affecting their own habitat. I’m not sure how meaningful diurnal differences are, just like I am not sure how a single point CO2 measurement in Hawaii means anything, or adjusted, averaged data from badly sited, uncalibrated and under-maintained surface stations in changing degrees of urbanisation mean anything. Let’s stick to what we can see, rather than what we can derive. Sea levels, volume of polar ice… I dunno. I studied bacteria, they are easier to keep tabs on than planets.

KAP, unless I’m reading the study incorrectly, there shouldn’t be a century long trend, just one from around the 50’s when all that awful manmade CO2 (sarc) began polluting the atmosphere. And yes, if AGW were in effect we should see the DTR decreasing – remember, we’re talking about the difference between the high and low temperatures. AGW predicts decreasing DTRs since CO2 is supposed to prevent the warming IR from escaping into the atmosphere.

Indeed, the entire thesis of CO2 caused global warming hinges on a decrease in DTR due to higher temperature night-time lows. A result which shows no trend at all is a rather significant counter result. As Einstein said (paraphrased since I never get quotes right) It only takes one counterexample to prove the whole thing wrong.

The graphs (at least the top one) of diurnal temperature at the cited page ask “Why the lag [in temperature between noon and 3-5PM]?” and the site has a big green ANSWER button that basically says it’s because the temperature is greatest at 3-5PM. I guess students couldn’t figure that out for themselves. Very educational.

Bill Illis says: May 19, 2011 at 7:40 am For the diurnal charts at the beginning of the post, just noting that the temperature change is exaggerated by quite a bit in these charts compared to a real-world station. There is far less change in the actual energy levels/temperature at the surface over a 24 hour period (between Max and Min), than should be expected.

I don’t know where Bill Illis lives, but the charts shown in Fall’s paper do seem to match with the places that I have lived. For example, using the historical data from weather.com (the easiest place I could located DTR data on short notice) here are the ranges of DTR data for the places that I have lived:

“The diurnal temperature range is simply the difference between the daily maximum temperature and daily minimum temperature, “diurnal” being a more impressive way of saying “daily”. ”

Ok, I’m lost here. If there is warming going on in the temperature record, then both the daily max and daily min temp could be (and I would think would be) higher by the warming offset, right? So I don’t think you’d see any warming using this method. What comes to mind is the Mauna Loa CO2 graphs that show a sinusoidal wave with an offset that is increasing steadily over time. Each successive year there is a higher Co2 level in the sine wave but there is also a higher ‘lower’ CO2 level in the sine wave but the delta between the high and low for each year is virtually the same.

Not really. While there would be a slow tendency for the next day to be warmer due to less heat lost the night before, the real effect of CO2 is supposedly its ability to prevent radiation of the warm surface to space. During the day there is some of that effect, but the heating of the sunlight coming in far overpowers the CO2 effect (the higher temps cause more energy to escape than cooler ones). At night there is no energy coming in so if there were no blocking of outgoing IR, the low heat capacity of air would tend to equilibralize (is that even a word?) with space rapidly making it quite cold. The greenhouse effect is our friend in that regard. But if the AGW theory is to be true, then the rising CO2 would cause the night time atmosphere to hold on to even more heat than it did previously thus rising minimum temperatures as compared to the daily maximum. Just as adding insulation to your house doesn’t do a thing for the maximum temperature your heater can put out (though it does affect the maximum differential to outside air, but that is a much more complicated problem with no analog to climate – space is always COLD), it does affect how long it takes for your house to reach thermal equilibrium with the outside air (ie how rapidly your house cools off), CO2 is this mechanism in the atmosphere according to AGW theory. My personal opinion is that while the broad brush strokes of the theory are correct, the amount of effect they accredit CO2 with is off by an order of magnitude.

This would also indicate that if there were no detectable change in the difference between the max and min, the rise in temperature is not likely caused by CO2, but by some other driver (the sun/ocean equilibrium anyone?)

kramer says: ““The diurnal temperature range is simply the difference between the daily maximum temperature and daily minimum temperature, “diurnal” being a more impressive way of saying “daily”. ”

Ok, I’m lost here. If there is warming going on in the temperature record, then both the daily max and daily min temp could be (and I would think would be) higher by the warming offset, right? So I don’t think you’d see any warming using this method. What comes to mind is the Mauna Loa CO2 graphs that show a sinusoidal wave with an offset that is increasing steadily over time. Each successive year there is a higher Co2 level in the sine wave but there is also a higher ‘lower’ CO2 level in the sine wave but the delta between the high and low for each year is virtually the same. What am I missing here???”

For one thing, the alleged effect of added greenhouse gases differs between night and day.

When we look at the hockey stick chart, we see the frightening fraction of a degree rise that will lead to a tipping point and runaway greenhouse effect that will turn us into Venus and boil away the rising seas and melt lead, etc.

It’s been pointed out that much of the drama is a result of the chart’s vertical scale. Perhaps someone more proficient at graphing from raw data than me might plot the world annual average temperature, not the anomaly, on a chart, along with the average high temp and the average low temp, three curves together. Plotting that way would force a reasonable scale that would put things in perspective.

Climate has 4 states: Warm, Cool, Wet & Dry.
A warm dry year has higher diurnals than a warm wet year, that is the highs are higher and the lows are lower therefore the range of day-night temps is greater.
Fixating on Warm vs Cool is misleading.

Most of the literature I’ve read has conceded that the DTR decline is likely consistent with increasing CO2 or AGW. Mostly the latter.

These results subtly undermine this little leg for the rise of AGW during the 20th century to stand on. Or at least we can hope that similar efforts elsewhere to find the best sited Temp stations will either confirm or deny this little toppling.

But if so many well-maintained stations cannot find an undeniable AGW signal, then maybe AGW isn’t very strong. Maybe the Enhanced Greenhouse Hypothesis is wrong.

Before I put pink bats in my roof, I did extensive temperature readings throughout the house, under the house, and outside. I live at 26deg 38sec Southern Latitude.

Summer (Feb) peaked between 1pm and 2pm reliably every day.
(March) peaked 1pm to 2pm, some times between 12pm and 2pm.
(April) spreak slightly further, typicaly 1pm to 2pm with variuous days starting a peak at 12pm and some days lagging the peak to 3pm.
(May) Peaks were generaly 12pm to 3pm every day.
(July) (one reading only) Peaked 1pm to 4pm.

These peaks were simply flatlined temperature readings, I read all measurements by eye to an accuracy of 0.5C.

All the features of the diurnal cycle are readily explained in terms of a linear system with capacitance, i.e., a low-pass filter. If the capacitance is increased, then the system output is REDUCED BILATERALLY in the transition range of frequencies between the pass-band and the stop-band, while the phase delay of peak output is INCREASED. Proponents of AGW misanalyze the effect of increased system capacitance in their attribution of increasing diurnal lows to increasing CO2 and fail to provide any evidence of any change in phase delay. What we observe in the urban dominated 20th century temperature records is mostly the effect of winter heating and other urban effects, rather than a sign of increased atmospheric capacitance.

“Maybe DTR really isn’t a robust signal of global warming, and maybe the discrepancy between models and observations is primarily a problem with the observations rather than the models!”

John, perhaps you could talk about the relationship between cloudiness and DTR under a presumption of global warming. Assuming the best observations show both an increase in mean temp and no secular trend in DTR that would point toward changes in cloudiness.. or have I got that wrong

“I do not believe that temperature, due to your discovered difficulties of measurement, and the fudging which seems to continue despite the arguments against such questionable practice, is a good indicator of human effect on climate. …”

May I, as a friendly gesture, recommend that, in future, one might better express oneself with shorter sentences and less circumlocution if one were just to …um, come right out and say what you mean?
:-)

As “sky” correctly noted, the diurnal chart can be easily explained in basic terms or ordinary heat transfer. More easily, there is a direct analogy (mathematical equivalence) between electrical circuits and heat transfer processes. Any electrical engineer would immediately recognize the chart as an ordinary non-ideal rectifier, with slightly nonlinear load. Thermal capacitor of surface-air gets “charged” when sun shines (through certain finite “resistor”), and discharges when not. The “leakage” is partly radiative, with addition of other resistive paths (convection/evaporation/precipitation). The temperature rises until the charge exceeds leakage, all very simple, regardless if this “leakage” is forth or any other degree, or even a constant. Therefore, the “answer” given in that lecture of department chief of Lyndon State College of Meteorology is fundamentally goofy and shows lack of in-depth understanding. I skipped across the rest of lecture, and it looks like a collection of cooking recipes to me. There are some good points presented, but overall I don’t think this class will prepare students for contributing to real science.

The confirmation of the trend found by all other scientists researching the instrumental temperature record is unsurprising.
The finding that in the best sited stations there is no change in the diurnal range confirms that the warming trend is NOT a solar effect and must be a ‘greenhouse’ effect.

Perhaps the reduced diurnal range in the ‘bad’ sites represents the greater effect of local CO2 levels that reduced the cooling at night?
-grin-

I wonder if you guys are perhaps all missing the point. I am missing whether or not it is maximum temperatures that are driving up the mean temperature or whether or not it is the minimum temeprature that are driving up mean temperature.
I would love to hear all your comments on the balls that are currently on my pool table:http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
(you do not want to know how much work this little compilation was)

KAP says:
May 19, 2011 at 8:36 am
But should we expect to see a century-scale trend? It’s clear that the primary cause of the 1880-1940 temp increase was due to solar effects rather than greenhouse,

Is it really? could you just clarify – is this the solar effect with lags or the solar effect without lags? I only ask because when solar activity moves in synch with temperature then it shows a clear correlation, but when solar activity declines, as it has since ~1991, while temperatures continue to rise then it’s because of the lag effect.

Is it really? could you just clarify – is this the solar effect with lags or the solar effect without lags?

Without lags. As far as I’m aware, there are no century-scale climate lags from solar forcing.

I only ask because when solar activity moves in synch with temperature then it shows a clear correlation, but when solar activity declines, as it has since ~1991, while temperatures continue to rise then it’s because of the lag effect.

The disconnect between declining solar activity and increasing temperatures since 1991 is due to increased greenhouse effect.

richard verney says:
May 19, 2011 at 5:51 am
What interests me in the best sited stations is:
1. What is the trend for maximum daytime temperatures (both annually and month by month).
2. What is the trend for minimum night time temperatures (both annually and month by month).
3. How does this correspond with their counterparts in the entire station series.

While the 30-year and 115-year trends, and all groups of stations, showed warming trends over those periods, we found that the minimum temperature trends appeared to be overestimated and the maximum warming trends underestimated at the poorer sites.

This discrepancy matters quite a bit. Wintertime minimum temperatures help determine plant hardiness, for example, and summertime minimum temperatures are very important for heat wave mortality. The use of temperature trends from poorly sited climate stations, therefore, introduces an uncertainly in our ability to quantify these key climate metrics.

While all groups of stations showed warming trends over those periods, there is evidence to suggest a higher level of uncertainty in the trends since it was found, as one example, that according to the best-sited stations, the 24 hour temperature range in the lower 48 states has no century-scale trend, while the poorly sited locations have a significantly smaller diurnal temperature range.”

Mean temperatures clearly increased for all qualities of surface station, and the difference they found is that at the best stations the difference between maximum and minimum temperatures did not show a trend, while at the poorly-sited stations, a trend toward less difference between minimum and maximum temperatures was detected. That is, they have a “smaller diurnal temperature range.”

As Dr. Pielke explains, a larger diurnal temperature range, which is what the best-sited stations exhibit, is indirectly bad for us because it is worse for plants including crops, but it is not as bad for humans directly, during heat waves. “Wintertime minimum temperatures help determine plant hardiness, for example, and summertime minimum temperatures are very important for heat wave mortality.”

Knowing these details will be invaluable in mitigation efforts, but by far the most important finding is that after all, just as Dr. Muller has found, the global mean temperature trend has been correct all along and is not an artifact of urban heat, surface station siting, or any other systematic bias.

The confirmation of the trend found by all other scientists researching the instrumental temperature record is unsurprising.
The finding that in the best sited stations there is no change in the diurnal range confirms that the warming trend is NOT a solar effect and must be a ‘greenhouse’ effect.

Perhaps the reduced diurnal range in the ‘bad’ sites represents the greater effect of local CO2 levels that reduced the cooling at night?

“…by far the most important finding is that after all, just as Dr. Muller has found, the global mean temperature trend has been correct all along and is not an artifact of urban heat, surface station siting, or any other systematic bias.”

Inasmuch as Fall et al. confine their findings to the US station records based on PRESENT-DAY siting ratings, this is a staggereging leap of illogic. If anything can be deduced physically from the lack of long-term trend in DTR is that the capacitance of the atmosphere has NOT changed. Thus whatever the course of long-term temperature changes, they are NOT due to any enhancement of the “greenhouse effect.” We have no comparable studies globally, where well-sited small-town stations with long, intact records are generally unavailable and urban records thus are used by default. Conclusions drawn from such records based on the pretense that systematic UHI bias doesn’t exist are scarcely science–let alone a wholly settled matter.

Hua Hin says:The finding that in the best sited stations there is no change in the diurnal range confirms that the warming trend is NOT a solar effect and must be a ‘greenhouse’ effect.

Perhaps the reduced diurnal range in the ‘bad’ sites represents the greater effect of local CO2 levels that reduced the cooling at night?”

Henry says
We have reasonable accurate data from weather stations all over world for the past 35 years. I do not trust most of the data from long before 1975 unless it can be explained exactly how the measurements were done and recorded. (like in the example of the station in Armagh – Northern-Ireland).

So far, the score on my pool table of global warming is as follows (I have just added the results of Bodo (in the arctic, Norway) and Honolulu (in the pacific, USA):

MAXIMA: rising at a speed of 0.04 degrees C per annum
MEANS : increasing at a speed of 0.02 degrees C per annum
MINIMA: no change at 0.00 degrees C per annum
HUMIDITY: decreasing at a rate of -0.02% per annum
PRECIPITATION: decreasing at a rate of -0.11 mm /month /year

This means that, on my pool table so far, the global warming trend that is observed on earth is natural (coming from outside) and is not caused by an increase in greenhouse gases.

If it had been the other way around, i.e. minimum temperatures rising, that pushes up the average temperature, (i.e heat being trapped), we should agree that the increase in greenhouse gases on earth was the cause.

Perhaps the most important question, “Is the mean temperature trend different from previous estimates?” is answered in the negative, albeit with an asterisk associated with the limited scope of the study. While negative results are useful, they’re also boring.

…These results suggest that the DTR in the United States has not decreased due to global warming, and that analyses to the contrary were at least partly contaminated by station siting problems. Indeed, DTR tended to increase when temperatures were fairly stable and tended to decrease when temperatures rose. Maybe DTR really isn’t a robust signal of global warming, and maybe the discrepancy between models and observations is primarily a problem with the observations rather than the models!

Anthony – are you in agreement with these statements by your co-author ?

It seems he is suggesting your paper is additional evidence towards AGW theory